This invention relates to a perfluorocarbon paint composition and, more particularly, to a perfluorocarbon paint composition for forming a fluorocarbon coating of an antistatic property and release property.
Fluorocarbon resins have excellent physical properties in release, heat resistance, chemical resistance, weather resistance, low coefficient of friction, and a fluorocarbon paint having a major constituent of a fluorocarbon resin is in use in a variety of fields. Despite these properties, a fluorocarbon paint fails to exhibit its inherent release property in some fields of application due to its high electrostatic property, which tends to cause foreign substances to be electrostatically attached to the surfaces of fluorocarbon coatings. What has been done in the past is to impart an anti-electrostatic property to the paint composition by adding thereto an electroconductive material, such as carbon blacks, carbon fiber powders, metallic powders, or fibrous potassium titanates coated with an electroconductive metal oxide.
Carbon black or a carbon fiber powder, which inherently has high water absorption properties, however, not only sharply increases its viscosity upon stirring, when added to a liquid fluorocarbon paint, but poses problems both in manufacture and applications, such as coagulation of the paint which takes place as the dispersion structure of the paint becomes unstable. When the same is added to a fluorocarbon paint in powder form, its apparent melt viscosity at the time of paint baking is so high that it has been difficult to satisfy the requirements of both forming uniform coating film and imparting sufficiently high electric conductivity thereto.
Powdered metals do not impart sufficient electroconductivity unless added in a large amount, and are expensive. Further, powered metals which have a high specific gravity tend to precipitate when added to liquid phase fluorocarbon paints, thus requiring repeated stirring while in use. Still further, there is a danger of explosion during the paint manufacturing process, depending upon the type and/or amount of the metal used. A further disadvantage is that the degree of improvement in conductivity of the paint is small in relation to the volume of added metal.
Fibrous potassium titanate coated with a electroconductive metal oxide has been brought into use more in recent years than the above cited electroconductive material. As disclosed in Japanese Patent Application Kokoku-Publication 1-38827, tin dioxide and antimony trioxide have been mainly used as electroconductive metal oxides. Due to its high oil absorbing property, however, potassium titanate, when added to a liquid fluorocarbon paint, tends to increase the viscosity of the paint and renders the dispersion structure thereof to be unstable, which easily creates coagulation of a paint. When added to a fluorocarbon paint, cracks tend to be formed in the coating after painting operation due to decreases in fluidity and heat melting property of the paint which are brought about by potassium titanate. In addition, the fibrous potassium titanate coated with an electroconductive metal oxide has insufficient electroconductivity due to the fact that the potassium titanate which is of less electroconductivity occupies a considerable proportion of the entire volume and must therefore be added in a large amount, with the result that the release property of fluorocarbon coatings is damaged.
The invention provides a fluorocarbon paint composition capable of forming fluorocarbon coatings of an excellent anti-electrostatic property and release property, without inviting the above drawbacks at the time of manufacture, storage and use.